1. Field of Invention
The present invention relates to a polarized light illumination device for uniformly illuminating a rectangular illumination area and the like by using polarized light polarized in the same direction, and to a projection display device using the polarized light illumination device. More particularly, the present invention relates to a structural technique of synthesizing light emitted from two light sources while aligning the polarization directions of the light.
2. Description of Related Art
A liquid crystal display device using a modulation element of a type that modulates a specific polarized light, such as a liquid crystal element, can utilize only one of two polarized light components included in light emitted from a light source. Therefore, there is a need to enhance light utilization efficiency in order to obtain a bright projection image. Since a projection display device using a single light source has a limited ability to enhance light utilization efficiency, the amount of light has been increased by using a plurality of light sources as a means for obtaining a bright image.
When simply a plurality of light sources are arranged, the area of a light-source image is increased by a plurality of times, and the angle distribution of light for illuminating an illumination area is also increased (the illumination angle is increased), whereas the amount of light per given area is the same as that in the case where a single light source is used. Consequently, in this case, the amount of light per given area is not practically increased even when a plurality of light sources are used.
If the amount of light is increased by using a plurality of light sources, when only one of two types of polarized light components, which are included in light emitted from the light sources, can be used, half the light is wasted, which reduces the effectiveness by half.